Frequency converters using diode mixers are well known in the art. The mixer performs up or down conversion between different frequency input signals. The frequencies which are output from the mixer are the modulation products which exist according to the heterodyne principle by which the mixer operates, wherein a pair of signals are applied to a nonlinear element such as a diode.
The present invention relates to low frequency diode mixers wherein the signal frequencies are low enough to permit coupling through transformer windings. Transformers are inherently bulky and costly to implement. The present invention evolved from efforts to provide simple, compact and low cost transformer circuitry in combination with a diode mixer.
The invention also evolved from efforts to improve isolation between the signals in the mixer. Separate mixer sections are provided to improve conversion efficiency and to minimize degrading influences, undesired coupling, parasitic induction, and the like, otherwise introducing distortion and other adverse performance characteristics.